A scanning exposure device is a device that exposes a substrate with light while relatively moving a light source unit and a stage supporting the substrate, and used, for example, for mask pattern exposure (see PTL 1) and exposure for photo-alignment (see PTL 2). The scanning exposure device includes the light source unit that is extended in one direction above a plane of the substrate, and, with a direction that intersects the extended direction of the light source unit being a scanning direction, the light source unit performs uniform exposure on a light irradiation area limited thereby, and moreover performs uniform exposure on a relatively large substrate by moving the substrate relatively to the light irradiation area.